Portable auxiliary power unit for trailers



4 Sheets-Sheet 1 7 Filed Dec. 1'8, 1939 I. W. SIMPKINS ETAL PORTABLE AUXILIARY POWER UNIT FOR TRAILERS March 18, 1941.

s. 3 E i 2 a? $1 lllll 15: W- Smmms EUGENE R. NELSON 3npentor$ Gttprneg March 18, 1941. I. w. SIMPKINS EI'AL PORTABLE AUXILIARY POWER UNIT 'F'OR TRAILERS Filed Dec. 18, 1939 4 Sheets-Sheet 2 ZSnventor S Gttorneg S m M m 5 c A A E UG ENE R. NELSON March 18, 1941- l. w. SIMPKINS EI'AL PORTABLEAUXILIARY POWER UNIT FOR TRAILERS ISAAC WS/MPk/M EUGENE R. llsLsoN Filed Dec. 18, I939 3maentor3 Gttorneg March 18, 94 1. w. SIMPKINS EI'AL PORTABLE AUXILIARY POWER UNIT FOR TRA'ILERS Filed Dec. 18. .1539 4 Sheets-Sheet 4 ISnventor 5: I544: W. .S/MPK/Ms "EUGENE 2. NsLso/v (Ittopneg Patented Mar. 18, 1941 UNITED STATES I PATENT OFFICE Isaac W. Simpkins and Eugene R.'Nelson, Charlotte, N. 0., assignors to Power Brake Company, Charlotte, N. 0., a corporation of North Carolina Application December 18, 1939, Serial No. 309,842

16 Claims. ,(Cl. 180-14) This invention relates to a portable auxiliary power unit for trailers which is adapted to be used in combination with a tractor when it is necessary to supply additional power. Very often the truck and tractor need an additional power unit, especially when a steep grade is encountered. Instead of placing the tractor motor in low gear and travelling up the grade at a very slow speed, the present invention contemplates placing an additional motor on the trailer and connecting this motor to a retractible set of wheels which are adapted to be raised or lowered at the will of the operator in the drivers seat of the tractor.

It is a well known fact that trucking companies operate transfer trucks over great distances, and in many cases, these trucks operate over ranges of mountains. As heretofore stated, the present invention is particularly adaptable for use on steep grades such as encountered in mountainous areas, but on the other hand when the truck is travelling over a relatively level country the need for additional power is not present. Therefore, by providing a portable power unit which may be easily removed and installed, the unit can be detached when the truck and trailer reach a level country and again be installed on the same or another trailer on a return trip when travelling in the opposite direction towards the mountainous area.

It is therefore an object of this invention to provide a motor vehicle comprising a tractor and a trailer, with the trailer having a retractible driving unit mounted thereon which unit has a raising and lowering mechanism controlled from the drivers seat in the tractor.

It is another object of this invention to provide a device of the class described with means controlled from the drivers seat for automatically actuating the throttle of the auxiliary power unit when a predetermined amount of pressure has been exerted between the retractible wheels and the ground. The reason for providing this type of throttle control means is to insure that the proper friction between the auxiliary wheels and the ground will be present before power is applied thereto. The proper friction will prevent skidding of the wheels and undueracing of the motor.

It is a still further object of this invention to the\ gears in the auxiliary power unit can be shifted. In other words the fuel supply to the auxiliary power unit is instantly cut oil when the operating valve in the drivers seat is actuated, after which the lifting means will automatically operate to slowly lift the auxiliary wheels from the ground. This lifting is delayed a short time so that in case the driver wishes to shift the gears on the auxiliary power unit, he can do so while the motor speed is low, and also without any fear of the wheels raising from the ground. Of course immediately after the gears are shifted, the operating valve is again actuated so as to renew the proper pressure between the auxiliary power wheels and the ground.

It is yet another object of the invention to provide means in an auxiliary power unit for trailers, whereby when the brakes are applied in the cab of the tractor, the flow of fuel to the auxiliary power unit will be diminished or entirely stopped.

Some of the objects of the invention having been stated, other objects will appear as the description proceeds, when taken in consideration with the accompanying drawings, in which Figural is a side elevation of portions of a tractor and a trailer embodying the present invention;

Figure 2 is a view of a typical diaphragm valve, with portions thereof shown in section, which valve is used for raising and lowering the auxiliary power wheels as well as for performing other functions;

Figure 3 is a sectional view through a portion of the trailer taken along the line 33 in Figure l, and showing in elevation on an enlarged scale the auxiliary power unit, with the wheels thereof in a retracted position;

Figure 4 is a plan view taken along the line 4-4 in Figure 3.

Figure 5 is a diagrammatic view showing the valve arrangement and the operating mechanism for raising and lowering the retractible unit;

Figure 5A is a sectional view through diaphragm motor I40 in Figure 5;

Figure 6 is a sectional view taken along the line 6-6 in Figure 5 through the sander valve;

Figure 7 is a sectional view through the check valve I38 showing the air exhausting port.

Referring more specifically to the drawings, the numeral l0 denotes a tractor having front wheels H and rear wheels [2. The front wheels are operated in a conventional manner by means of a steering wheel l3 which is mounted upon the upper end of a steering column Id. The operator of the tractor is adapted to be seated in a seat l5 during the operation of the tractor.

The rear portion of the tractor has pivotally secured thereto as at l1, the foremost end of a trailer bed l6. This trailer bed can be of any desired length and has its trailing end supported by wheels l6 which are rotatably mounted on the ends of axle 26. Disposed between the axle 26 and the bed i8, are suitable conventional springs 2|, the ends of which are adapted to support brackets 22 which in turn support side channel members 23 and 24. The channel members 23 and 24 are preferably constructed of steel so as to form a rigid framework for the trailer member. By referring to Figure 3, it will-be seen that the side channel members 24 run longitudinally of the trailer member and have transversely disposed channel members 26 disposed there between.

In order to furnish the desired auxiliary power for this trailer so that the motor within the tractor l6 can 'be assisted while the tractor and trailer are moving up-grade, it is necessary to suspend beneath the trailer framework a power unit in a manner such as shown in Figures 1 and 3. It is here seen that the transverse channel members 26 have hanger rods 26 secured thereto which rods support the intermediate portion of a motor framework 36; whereas another hanger rod 3| is adapted to have its upper end connected to another transverse channel member 26 and to have its lower end connected to the frontportion of the framework 36. The upper ends of the hanger rods 26 and 3i have nuts 23a and 3|a respectively secured thereon in such a manner that they may be easily detached when I it is desired to remove the framework 36' from connected as at 35 to each bracket 22 is a second beneath the trailer.

An additional means must be provided for connecting the framework 36 to the rear axle 26 so that when the auxiliary wheels are lowered, the power from engine 39 exerted thereby will be immediately transmitted to the trailer unit. This connection comprises horizontally and rearwardly disposed rods 34 which have the foremost ends thereof connected to the lower intermediate portions of hanger rods 29 and the rear or trailing ends connected as at 35 to bracket 22. Also framework 36 at point 33, therefore the front ends of the rods 34 can be connected very close to this pivot point. Hence any power from engine 33 that is transmitted to the frame 36 can be immediately transmitted by way of the rods 34 and 36 to the rear axle 26.

The framework 36 normally supports a source of power such as an internal combustion motor 33, said motor having a transmission 46 to which a drive shaft 42 is connected as at 43 (Figure 3). The trailing end of the drive shaft 42 is connected as at 44 todifierential shaft 45 of differential housing 46. The drive shaft 42 has the conventional splined feature to permit free pivotal movement as to pivots 38, 56, .5i and 35. By observing Figures 3 and 4 it is seen that the housing 46 has wheels 41 at each end thereof which are driven in the well known manner by shafts 42 and 45. The driving shaft between the transmission and differential is constructed in a conventional manner so that it may occupy th angular position in the manner shown when the wheels 41 are raised from the ground.

Radius rods 46 are provided for keeping the housing 46 in spaced relation to the framework 36, said rods having ball and socket joints 56 and 5| secured to the front and rear ends thereof respectively which assist in supporting the wheels 41 when raised by a mechanism which will be hereinafter described.

The upper side of the housing 46 has pivoted thereto as at 53 a plurality of springs 54, and the front ends of these springs are secured to the upper side of a squared axle member '55, the ends of said axle member being restricted as at 56 and are pivoted in the framework 36.

- Extending forwardly from the intermediate portion of the squared axle 55 is a lever arm 56, to which is pivoted the lower end of an operating rod 53 as at 66. The upper end of this rod penetrates a housing 6| of diaphragm assembly I 16 which in turn has secured thereto a cap member 62 (see Figures 2, 3 and 5). Between the members 6| and 62 is secured the rim of a flexible diaphragm member 63 and the intermediate portion of this diaphragm member is secured to the uppermost end of the rod 59. The housing members 6| and 62 are secured together by any suitable means such as bolts 64. Normally the diaphragm member 63 is forced in the position shown in Figure 2 by any suitable means such as a compression spring 65 within the flexible diaphragm member 63 will move to the right gradually increasing the size of the chamber 66 and diminishing the size of chamber 63 to the right of the diaphragm member.

The diaphragm membershown in Figure 2 is typical of all of the diaphragms employed to carry out the various operations to be hereinafter described in connection with the auxiliary power unit. In order to keep the various diaphragm motors distinguished from each other, a different reference character will be employed, yet it is to be understood that the internal structure and the principle of operation of all of them are essentially the same.

The structure employed in the diaphragm motors for raising the wheels 41 from the ground will be broadly designated by the reference character 16. r g

In order to lower the wheels 41, two suitable assemblies 1| are employed which are identical to the diaphragm assembly 16 recently described. These assemblies 1l, likewise have rods 53 extending therefrom, the ends of which are secured as at 12 to brackets 13. The brackets 13 are mounted upon the upper side of the springs 54 and are also rigidly secured to the axle 55. Upon the introduction of air into the assemblies 1| their respective rods 59 are moved to the right in Figures 3, 4 and 5 to rotate arms 13, axle 55 and springs 54 in a clockwise manner in Figure 3 to cause the wheels to be lowered. 0n the other hand, when it is desired to raise the wheels, air is exhausted from diaphragm assemblies 1| and at the same time air is introduced into the diaphragm assembly 16, which, in turn, will move parts 13, 55 and 54 in the opposite direction from that above described to rotate the axle in a counterclockwise manner to raise the wheels.

The operation of the diaphragm motors II and 'II,, as well as other operations, are controlled from the drivers seat I5 of the tractor unit. A hand valve for controlling these valves is indicated by the reference character I4 and is secured to the steering column I4. This hand valve is supplied with air through a suitable supply pipe I5 which pipe has the other end thereof communicating with a compressed air supply tank I8. The valve is provided with a suitable hand lever I8 which has one end thereof secured to the upper end of a spring cage I8, said cage being threadably secured within a cover 88, said cover being secured to the top of a casing 8| in which the valve control mechanism is located. Cover 88 and casing 8I have slidably mounted therein a piston assembly 83, which assembly has a piston 84 secured on the lower end thereof and is normally forced downwardly by means of a graduating spring 85. The lower central portion of the piston assembly has vertically disposed port 88 therein having a transversely disposed port 81 communicating therewith through which the air is allowed to pass when the pressure is desired to be released. The port 88 normally contacts the closure button 88 which projects upwardly from the upper side of an inlet. valve 88. This inlet valve is normally forced upwardly by inlet valve 88 to prevent the air from flowing from chamber 8| into chamber 82 when the pressure within the chamber 8 I is equal to or greater than the downward pressure exerted by the spring 85 upon the piston assembly 83.

A return spring 88 is provided directly below the piston assembly 83 to return it when the graduating spring 85 is not compressed. Let us assume that it is desired to let air pass from pipe I5 and the chamber 88 into the chamber 82 and then to pipes 83 and to relay valve 84. In this case, the hand lever 18 is operated or turned which will screw the spring cage I8 downwardly and will apply pressure to the spring 85 which, in turn, will force piston assembly 83 downwardly against button 88 to close outlet port 88 and prevent the air from passing outwardly through ports 81 into space. Upon further turning of the spring cage, valve 88 is forced downwardly to allow the air to pass through port I88 from chamber 8| into chamber 82. The air continues to flow from chamber 8I into chamber 82 until the pressure within chamber 82 has become sufiicient to force the piston assembly 83 and piston 84 upwardly against compression spring 85, so that valve 88 will close the port I88. At this time, the button or closure means 88 will also be closing the valve or port 88 which will prevent any outflow of the air from the chamber 82. It is therefore seen that the greater the pressure exerted upon the graduating spring by rotation of handle I8, the greater the amount of pressure will be necessary within chamber 82 to cause the valve 88 to close port I88; consequently, it is seen that the pressure within the pipe 83 and relay valve 84 can be varied any desired amount. I

In the drawings, the button or closing means 88 is shown slightly removed from the ports 88, and in this position the air will be allowed to move upwardly from the chamber 82 through ports 88, 81 and IN into space. This position is only maintained when it is desired to entirely relieve the pressure from relay valve 84.

A suitable lock ball I83 is provided which is adapted to be resiliently pressed into suitable notches such as I84, cut in the periphery or exterior surface of spring cage I8. resiliently pressed against the side of the spring cage by any suitable means such as compression spring I88 and is confined in the cavity by means of a nut I88. It is quite evident that a plurality of notches I84 may be provided so that when the spring cage has been rotated to the desired point it will fall into one of these notches and yieldingly hold the spring gauge in position. Where the threads on the spring gauge are properly pitched, the members I83 to I88 may be entirely eliminated, but it is preferable to have notches so that the operator may be assured that the spring cage will not move upwardly to relieve the pressure after it has once been properly applied.

It will be seen by referring to Figure 1 that the pressure tank I8 is disposed upon the tractor, whereas a similar pressure tank I88 is carried by the trailer I8. These tanks have pipes IN and I 82 respectively leading therefrom in which check valves I 88 and I88 are installed. The two pipes I8I and I82 merge into a single pipe II8, the other end of which is connected to air com pressor III.

The trailer tank I88 has'a pipe II2 leading therefrom, the other end of which is connected to the lower side of relay valve 84 and is adapted to communicate with a chamber II4 therein. The special function of the relay valve 94 is to quickly transmit the air pressure from the trailer tank I88 to the operating valves I8, I I, and other valves-which will hereinafter be described. When it is desired to quickly transmit this pressure, the handle I8 inthe operating valve I4 is operated as previously described, at which time the air from the tractor tank I8 will pass therethrough and enter the relay valve 84 by means of the connecting pipe 83.

The lower end of the pipe 83 communicates with a chamber H5 in the upper portion of the relay valve (Figure 5). Disposed in the lower portion of the chamber 5 is a flexible diaphragm II8, which diaphragm normally rests upon a piston III, said piston being mounted for vertical sliding movement in a cylinder H8. The flexible valve I I8 also is adapted to rest upon the upper rim of the cylinder II8. Piston III has a centrally disposed stem I28 extending downwardly therefrom which stem penetrates a bore I2I which is larger than the stem. This bore is disposed in partition I22 which separates chamber II4 from a chamber I23. It will be noted that the stem I28 has a valve I25 therearound which normally closes the port I2I under the force of a compres- This ball is sion spring |2"I therebelow. A compression spring I28 is disposed within chamber I I5 and above the flexible diaphragm II8 for normally holding the top edges of this diaphragm in position, said outer edges being adapted to cover an annular groove I38 which surrounds the cylinder 8. Groove I38 communicates with chamber I3I, said chamber having an outlet port -I32 communicating therewith. When it is desired to transmit the pressure from the trailer tank I88 into the lowering diaphragm valves II it is only necessary to turn the handle I8 of the operating valve 14 in the manner previously described. This will allow the air from the tractor tank 18 to enter the compartment H5 and when the pressure is built up within this compartment the central portion of the diaphragm II8 will move downwardly along with the piston II'I forming an upper concave surface. This bulging em will not cause the outer edges of the diaphragm to become unseated, but instead the annular groove I05, will remain covered, Upon the downward movement of the central portion 01 the diaphragm, I I5, the piston I11 and piston stem I20, the valve I25 will likewise move downwardly to open the port ,I2I. Upon the opening of this port the air from the tank I00 will immediately rush into chamber II4 upwardly through port HI and into compartment I23. From the compartment I23 the air will exhaust into pipe I35, pipe I31, check valve I30, pipe I39, and into diaphragm motors H which will be actuated to cause the squared axle 15 to rotate in a clockwise manner in Figures 1, 3 and 5 to allow the auxiliary traction wheels I41 to be moved downwardly into contact with the ground.

The air from the cylinder I00 also flows through the relay motor 84 and through pipe I06 into a diaphragm valve I40, which valve has a piston rod 50 extending therefrom, the outer end of which is connected to a throttle actuating bell crank I. The other leg of the bell crank I4I actuates a throttle control rod I42. The construction of the motor is essentially the same as motor 10 in Figure 2, except the spring 55 within the housing is omitted; however, a spring 20I is secured to hell crank I for loading the diaphragm 53 within thecasing (Figure 5A). The amount oi tension in the spring and also the initial load upon the diaphragm is varied by means of bolt 202 to which the other end of the spring is attached. The diaphragm motor I40 is preferably spring loaded initially so that it requires a pressure of approximately 50 pounds of air to start operating it. This will allow sumcient pressure to be exerted between the traction wheels 41 and the ground before the throttle to the engine on the auxiliary power unit is actuated. Therefore. -it is seen that as the pressure in the relay valve is increased, there is a corresponding increase in the amount of gas fed to motor 33,

A slightly diflferent means; is employed for raising the wheels 41 out of contact with the ground when the additional power of engine 00 is not needed. a v

By observing Figure 5 it is seen that the pipe II2 has a pipe I45 communicating therewith, the other end of which communicates with chamber I41 of a valve I40 (Figure 6). The valve I40 essentially comprises three members, namely, a base member I40, a cover I50, and a cap I5I, said cap member being disposed within the cover I and rotatably resting against lower side or the base member I49. The cap I5I is normally held in position by means of a compression spring I52. The central portion of this cap member I5I has a stem I53 extending upwardly therefrom and through the base member I40. The upper end of the member I53 has a lever I54 secured thereto. The lever I54 has a rod 59 of a standard diaphragm. motor I55 secured thereto as at I51. Leading to the diaphragm motor I55 is a pipe I50, the other end of which communicates with the interior of pipe I39, previously described, and which pipe receives air from the relay valve chamber I23.

Of course when the air is turned onto the pipe I39 and valves 1| to cause wheels 41 to be lowered, the air is simultaneously introduced into the diaphragm motor I50 by way of pipe I50, and

this will rotate the lever I54 away from the observer (Figure 5) in a counter-clockwise manner to provide a passageway through which the air from the raising diaphragm 10 and pipe I50 may mesa-11c be exhausted. The raising diaphragm 10 has one end or pipe I50 leading therefrom, the other end oi said pipe being connected to the sander valve I40 as at port I00. Normally the port I00 in the sander valve is closed by means of the cap plate "I therebeneath, that is, the port is closed when the wheels :41 are in raised position to prevent the oi the members I54 and valveI50, thereby causing an arcuate groove IOI which is disposed in the top of the cap member I5I (Figure 6) to communicate with the outlet port I00 of pipe I59 and also communicate with the port I55 in the base member I45. However, when it is desired to maintain the pressure within the lifting diaphragm motor 10, as in case when the wheels are being lifted (mm the ground, the pipes I45 and I50 communicate with each other by way or the valve-chamber I41. This communication is possible because the'air will be exhausted from valve I 50 and at that time cut-away portion I5Ia within the cap member I5I will not close either of the outlets to the respective pipes. Ordinarily, the diaphragm I50 has a conventional spring I66 therein, such as shown in Figure 2, but in order to supplement this spring pressure with an additional positive force to insure the proper actuation orthesander valve I40, an additional spring I51v has beenprovided.

Whenever the wheels 41 are raised, it is necessary as previously stated, to release the air from the diaphragm valves 1|. This pressure release however is not instantaneous, but instead it is allowed'to escape slowly through a small port or opening I30a in the check valve I38 (Figure '1 The time ordinarily necessary to allow the pressure to escape from the diaphragm 1| through the port is about a minute and a half, but it should be borne in mind that when the valve 14 within the drivers seat is actuated to produce the operation, that the air from the chamber I20 in the relay valve 04 is immediately released. This release takes place when the air is exhausted from the upper chamber I I 5, thereby allowing the valve I25 to close the port IN and at the same time return flexible diaphragm member II5 to normal position. when the pressure is released from the upper chamber leaving an upward air pressure in the lower chamber, the air from this lower chamber will force the outer periphery of the diaphragm member I I5 upwardly to flow into annular groove I00 and then outwardly to exhaust port I32. .Due to the fact that .it'takes considerable time for the air to leak out from the diaphragm chambers 1 I, the wheels 41 will remain in contact with the ground; however, the air will instantly-exhaust from throttle diaphragm andslow down the motor should the driver merely.wish to 'change the gears in the auxiliary power unit. This gear changing mechanism for the auxiliary motor is conventional and is also operated from the drivers seat in a conventional manner.

Briefly the operation of the apparatus is as follows: To lower the device, the valve 14 is actuated allowing air to pass therethrough' from cylinder 10 into relay chamber 5, which will operate the diaphragm II5 therein to cause the air from the trailer cylinder I00 to also enter the relay valve and to be exhausted therefrom into the lowering diaphragm II to cause the wheels to be lowered and at the same time to admit air time, the lowering is effected, air is introduced into diaphragm valve I56 which will rotate the handle I54, of the valve I48. This will rotate the cap member I5I therein in a counter-clockwise manner in Figure 5, causing the port I80 of pipe I59 and the exhaust port I65 in the sander valve to communicate with each other which will relieve the air pressure from the raising diaphragm motor 10. a

To raise the wheels 41 the handle 18 of hand valve 14 is turned in the opposite direction thereby releasing the pressure from the upper chamber I I5 and allowing the air to escape from the chamber I23 therebelow as well as from pipes I38, I31 and I58 and diaphragm I58. The air, at the motors 1I through pipes I39 and opening I39a in check valve I38. At this time, the air from the trailer cylinder I00 will move directly through pipes H2 and I45, through valve I48 and into the diaphragm cylinder 18 to cause the wheels 41 to be raised out of contact with the ground. The valve I48 is known commercially as a sander" valve, but is used as a three-way valve in the present instance for admitting and exhausting air from diaphragm motor 10.

There are occasions when it is desired to automatically cut off the gasoline or fuel supply from the auxiliary motor 39 when the quick application of brakes is necessary. In order to insurethat means will be provided for automatically. cutting off the gasoline to the auxiliary motor upon application of pressure upon the brake pedal, a suitable air line IN is provided, one end of which is connected to tractor tank 18 and its other end connected to a standard application air valve I12. An operating rod I13 is disposed between valve I12 and a conventional brake pedal I14, said rod being adapted to open the valve when it is moved to the left (Figure 5) upon applying pressure to the brake pedal. When valve I12 is opened, the compressed air will flow from tank 16 into this valve from whence it will flow through a line I15 and thence to a line I18 which supplies air to cylinder I11. The line I15 has leading therefrom another line "So which supplies air for operation of conventional trailer brake connections, not shown. The cylinder I11 has a piston I18 therein which will be forced outwardly or to the right in Figure 5, thus causing plunger rod I19 toengage lug I of hand lever 18 to thereby cause the spring cage 19 to rotate and exhaust the air from throttle diaphragm I40, and thereby reduce the motor 39 to idling speed. In other words, when thebrake lever I14 is pressed, the service line I15 has compressed air admitted therein which air will be transmitted to cylinder I11 to cause hand valve to be automatically operated to cut off the gas to motor 39. Upon release of brake pedal I 14, the air is automatically released from cylinder I11 through the conventional release port of application valve I12. The line I15 furnishes air to the conventional front and rear wheel diaphragm motors I95 and I98 respectively, through pipes I8I and I8I a, respectively. These motors are similar in construction to diaphragm motor 10 (Figure 2) and each has a rod 59 extending therefrom which operates brake lever I91 and I98, said brake levers being adapted to operate brakes I99 unit is most desirable. 29 and 3| are detachedjrom the trailer body the and 200 on the front and reartractor wheels,-

respectively.

It is desirable to have the auxiliary power unit mounted on suitable wheels so that when it is removed from a trailer unit, it can be rolled about from place to place. In other words, a portable When the hanger rods rear wheels 41 of the unit are lowered to dotted line position as shown in Figure '3. Then a front swivel wheel I82 is lowered to the ground to hold the front end of the unit in elevated position. This swivel wheel is rotatably mounted in a bracket I83 which bracket has. a vertically disposed grooved shaft I84 secured to the upper end thereof. This shaft I83 penetrates the front end of the framework 30 and the grooves therein are engaged by the gear I85 which gear also meshes with a worm I36 on crank I81. By turning the crank I81, the shaft I83 and its associated wheel I92 can be raised or lowered to the desired position. When the unit is mounted on a trailer the wheel I82 is raised .to elevated position as shown in the drawin s, so as to move it out of contact with the ground.

Especial attention is called to the position of the wheels 41 of the auxiliary power unit relative to the trailer wheels I9. It will be noted that the wheels '41 are mounted at the ends of a very short differential housing thereby making ing the distance between the wheels correspondingly short. Also the wheels 41 of the unit are symmetrically positioned along the longitudinal center line of the trailer in advance of the trailer axle 20, but at the same time, as close to the axle as is consistent with the proper raising and lowering operations. Byp'roviding a prime mover having wheels whose gauge is very much narrower than the gauge of the trailer wheels and by locating the prime mover wheels in advance of the trailer axle so that they occupy an overlapping relationship to the trailer wheels, there is very much less sidewise drag of the unit wheels when the trailer turns a curve.

Also since the unit is suspended at three points, namely by one hanger rod 3| at the front and two hanger rods 29 near the rear, there is a limited amount of sidewise flexibility of the unit which is very essential when the trailer and unit are turning curves. In other words, when a lateral or sidewise thrust is exerted upon the unit wheels 41, the entire unit will be allowed to adlust itself to this thrust and thereby materially reduce the drag on the wheels.

In the drawings and specification there has been set forth a preferred embodiment of the invention, and although specific terms are employed, they are-used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the appended claims.

We claim:

1. In a trailer adaptedto bepivotally secured at its front end to the rear end of a tractor and having wheels supporting the rear end thereof,

a framework having a prime mover mounted therein, a traction wheel mounted on the framework, means normally holding the traction wheel prime mover until a predetermined amount of pressure has been applied to the traction wheels of the framework to hold them in contact with the roadway, and means for raising the tractor wheels of the framework from contact with the roadway.

2. In a trailer adapted to be pivotally secured at its front end to the rear end of a tractor and having wheels supporting the rear end thereof, a detachable framework having a prime mover mounted therein, a plurality of traction wheels mounted on the framework, means normally holding the traction wheels out of contact with the roadway, means controlled by the operator of the tractor for lowering the traction wheels and exerting the necessary pressure thereon to hold the same in contact with the roadway, driving means between the prime mover on the framework and the traction wheels, means preventing operation of the prime mover until a predetermined amount of pressure has been applied to the traction wheels of the framework to hold them in contact with the roadway, means for raising the tractor wheels of the framework from contact with the roadway and means controlled by the application of brakes on the tractor for preventing output of power by the prime mover.

3. In a trailer adapted to be pivotally secured at its front end to the rear end of a tractor and having wheels supporting the rear end thereof, a framework having a prime mover mounted therein, a traction wheel mounted in the framework, means normally holding the traction wheel out of contact with the roadway, means controlled by the operator of the tractor for lowering the traction wheels and exerting the contact with the roadway, driving means between the prime mover on the framework and the traction wheels, means preventing operation of the prime mover until a predetermined amount of pressure has been applied to the traction wheels of the framework to hold them in contact with the roadway, means for raising the tractor wheels of the framework from contact with the roadway, and means for reducing the power of said prime mover upon the reduction of pressure below said predetermined amount between the traction wheels and the ground.

4. In a trailer adapted to be pivotally secured at its front end to the rear end of a tractor and having wheels supporting the rear end thereof, a framework having a prime mover mounted therein, a traction wheel mounted in the framework, means normally holding the traction wheel out of contact with the roadway, means controlled by the operator of the tractor for lowering the traction wheels and exerting the necessary pressure thereon to hold the same in contact with the roadway, driving means between the prime mover on the framework and the traction wheels, means preventing operation of the prime mover until a predetermined amount of pressure has been applied to the traction wheels of the framework to hold them in contact with the roadway, means. for raising the tractor wheels of the framework from contact cation of brakes on the tractor for preventing output of power by the prime mover, and means for reducing the power of said prime mover upon the reduction of pressure below said predetermined amount between the traction wheels and the ground.

necessary pressure thereon to hold the same in l with the roadway, means controlled by the appli- 5. In a trailer having its front end pivotally supported by the rear end of a tractor and having its rear end supported by wheels, a unit securedto the lower side of the trailer frame and having an internal combustion engine mounted therein, a pair of traction wheels supported by the framework, means controlled by the driver of the tractor for raising and lowering ,the traction wheels of theunit out of and into contact with the roadway, means for automatically delivering an increased amount of fuel to said engine when the traction wheels have a predetermined amount of pressure applied thereto to hold them in contact with the roadway, means controlled by the driver of the tractor for regulating the fuel supplied to the engine of the unit and means controlled by the brake applying means of the tractor for reducing the supply of fuel to the engine of the unit.

6. In a trailer having its front end pivotally supported by the rear end of a tractor and having its rear end supported by wheels, a detachable unit secured to the lower side of the trailer frame and having an internal combustion engine mounted therein, a pair of traction wheels pivotally supported by the framework, means controlled by the driver of the tractor for raising and lowering the traction wheels of the, unit out of and into contact with the roadway, means for automatically delivering an increased amount of fuel to said engine when the traction wheels have a predetermined amount of pressure applied thereto to hold them in contact with'the roadway, means controlled by the driver of the tractor for regulating the fuel supplied to the engine of the unit, means controlled by the brake applying means of the tractor for reducing the supply of fuel to the engine of the unit, and means for automatically reducing the flow of fuel to the engine of the unit before the traction wheels of the unit are raised from contact with the roadway.

7, In a trailer having its front end pivotally supported by the rear end of a tractor and having its rear end supported by wheels, a unit secured to the lower side of the trailer frame and having an internal combustion engine mounted therein, a pair of traction wheels supported by the framework, means controlled by the driver of the tractor for raising and lowering the traction wheels of the unit out of and into contact with the roadway, means for automatically delivering an increased amount of fuel to said engine when the traction wheels have a predetermined amount of pressure applied thereto to hold them incontact with the roadway, means controlled by the driver of the tractor for regulating the fuel supplied to the engine of the unit, means controlled by the brake applying means of the tractor for reducing the supply of fuel to the engine of the unit, and means for automatically reducing the flow of fuel to the engine of the unit before the traction wheels of the unit are raised from contact with the roadway.

8. In a tractor and trailer, an auxiliary power unit mounted on the trailer and having traction wheels and including an internal combustion engine for driving the traction wheels, means normally holding the traction wheels out of contact with the roadway, means controlled by the driver of the tractor for lowering the tractor wheels into engagement with the roadway, means for supplying fuel to the internal combustion engine,

9. In a tractor and trailer, said tractor having brakes'associated with its wheels, an auxiliary power unit mounted on the trailer and having traction wheels other than the wheels of the trailer, a prime mover mounted on the unit and having a driving connection with the traction wheels of the unit, means controlled by the driver of the tractor for controlling speed of the prime mover of the unit, means operable from the drivers seat in the tractor for lowering and raising the traction wheels of the unit into and out of engagement with the roadway, respectively, and means operable automatically by application of the brakes on the tractor for diminishing the amount of power generated by the prime mover. 10. In a trailer adapted to be pivotally secured at its front end to a tractor and having wheels at its rear end for supporting the trailer, an auxiliary power unit detachably connected to the lower side of the trailer and having a prime mover mounted thereon and having traction wheels driven by the prime mover, means for normally holding the traction wheels of the auxiliary power unit out of contact with the roadway, means controlled by the driver of the tractor for lowering said tractor wheels of the imit into contact with the roadway and for controlling the amount of power delivered by the prime mover on the unit, means preventing the generation of substantial power by the prime mover on the unit until after a predetermined amount of pressure has been applied to the tractor wheels of the unit to hold it in contact with the roadway, and means operable automatically upon the application of the brakes on the tractor by the operator for diminishing the amount of power generated by the prime mover on the unit.

11. In a trailer adapted to be pivotally sec at its front end to a tractor and having wheels at unit into contact with the roadway and for controlling the amount of power delivered by the prime mover on the unit, means preventing the generation of substantial power by the prime mover on the unit until after a predetermined amount of pressure has been applied to the tractor wheels of the unit to hold it in contact with v the roadway, and means for varying the amount of power furnished by said prime mover in directproportion to amount -of pressure between the wheels of the unit and the ground.

12. In a trailer adapted to have its front end secured to a tractor and having wheels at its' rear end for supporting the rear end of the trailer, a quickly detachable auxiliary power unit secured to the trailer and having a prime mover thereon and having traction wheels driven by the prime mover of the unit, and means within control of the driver of the tractor while the tractor and trailer are moving over a roadway for controlling the amount of power generated by the prime mover of the unit and for raising and lowering the tractor wheels of the unit, and means operable automatically by the application of the brakes by the driver of the tractor for reducing substantially the amount of power generated by the prime mover of the unit.

13, In a trailer adapted to have its front end pivotally secured to the rear end of a tractor and having wheels supporting the rear end of the trailer, a quickly detachable auxiliary power unit secured to the lower side of the trailer in advance of the wheels of the trailer and having an internal combustion engine carried thereby, a pair of traction wheels carried by the unit and being movable vertically with respect to the unit, means normally holding the traction wheels of the unit out of contact with the roadway, means controlled-by the driver'of the tractor while the tractor and trailer are moving over a roadway for lowering the traction wheels of the unit into contact with the roadway, and after said'tractor wheels have been lowered a predetermined amount, for automatically supplying fuel to the internal combustion engine of the unit in proportion to the exerted pressure and for also allowing the tractor wheels of the unit to be raised out of contact with the roadway after the fuel supply to the internal combustion engine has been diminished, and means operable automatically upon application of the brakes in the tractor for diminishing the fuel supply to the engine of the unit-without allowing the wheels of the tractor to be raised.

14. A truck, including supporting wheels and driving means therefor, and a semi-trailer for attachment to the truck, the semi-trailer having wheels supporting the rear end thereof, an auxiliary 'power imit including a motor suspended having traction wheels and means for normally holding them in elevated position, driving means between the motor of the unit and the traction wheels therefor, means controlling the operation of the motor of the unit and the raising and lowering of the tractor wheels of the unit, and means operable automatically upon the application of brakes by the operator of the tractor for substantially decreasing the power generated by the motor of the unit.

15. A truck including supporting wheels and driving means therefor and a semi-trailer for attachment to the truck, the semi-trailer having wheels supporting the rear end thereof, an auxiliary power unit including a motor and vertically tion of brakes to the .truck by the operator thereof for decreasing the revolutions per minute of the motor of the unit. I

16. In a tractor and trailer, wheels supporting the rear end of the trailer, an auxiliary power unit suspended beneath the trailer and having traction wheels mounted thereon for vertical movement, an internal combustion engine having a driving connection with the traction wheels of below the load platform of the trailer, said unit im determined amount of downward pressure has been applied to the traction wheels of the unit. said increase being in direct proportion to the applied pressure, said controlling means including means for raising the traction wheels out of contact with the roadway and for substantially diminishing the amount oi fuel supplied to the engine of the unit before the traction Wheels 5 are raised out of contact with the roadway.

ISAAC W. SIMIPKINS. EUGENE R. NELSON. 

